Low-Temperature Plasma Etching of Copper Films Using Ultraviolet Irradiation

Abstract

Inductively coupled plasma etching of copper under ultraviolet (UV) irradiation is proposed. We achieved an etch rate of about 300 nm/min at room temperature using Cl-2/N-2 (or Cl-2/Ar) gas mixture. UV light irradiation lowers the activation energy of copper etching from 1.6 eV to 0.12 eV and enhances CuCl desorption, which makes it possible to etch copper at low temperatures. The etch rate increases almost linearly with increasing UV light intensity, and then saturates at high UV intensity. It is concluded that the etching process is not a simple thermal process, but a kind of photodesorption of CuCl due to ultraviolet irradiation. This etching method will bring us closer to high-resolution copper metallization.